1. Field of the Invention
The invention relates to a shoe, particularly, to a shoe which has an ergonomic insole unit incorporated therein.
2. Description of the Related Art
Conventional lasts for making shoes generally have planar bottom faces at heel regions. Although manufacturers are aware that the wearers"" heels are substantially semicircular at their bottoms, lasts used in lasting heels are not provided with a bottom having the same profile as that of the wearer""s heel since the bottom profile of the lasts cannot accommodate a heel lasting machine. A heel lasting machine normally has a wiper blade that traverses the bottom face of a last so as to fold and press a lower margin of an upper over and against an insole supported by the last bottom. As the wiper blade traverses linearly and immediately below the last, the last is provided with a planar surface (1A), as shown in FIGS. 1A and 1B, so as to avoid interference with the movement of the wiper blade. If the last bottom is convex, the insole and/or the bottom margin of the upper can be damaged by the wiper blade, and difficulties will be encountered in the heel lasting process.
Since the last bottom is planar, the insole used in a lasted shoe is usually planar. The planar insole is insufficient to cushion and comfort the wearer""s foot since it does not contact and support sufficiently all parts of the foot other than the foot palm and the heel. Stress concentration thus occurs at the foot palm and the heel due to the weight of the wearer""s body. The heel can even get injury at the calcaneus in case of prolonged wearing of the shoe incorporating such planar insole.
It is known to provide a last with a bottom face conforming to the bottom of the wearer""s foot in manufacturing a sandal since no heel lasting machine is used in making the sandal. An example of such a last is shown in FIG. 2A and 2B at 2 and has a convex bottom face 2A. A sandal 3 made by using the last 2 is shown in FIG. 3 and has a foot bed 31 which can be in proper fit with the wearer""s foot to support all areas of the foot bottom so that the weight of the wearer can be distributed to all parts of the foot bottom. Such a foot bed can not be provided in shoes, such as sport shoes, walking shoes, etc., which are produced via heel lasting machines.
It is usual to provide a shoe with a reinforcement piece, such as, a counter or stiffener, at the heel section of the shoe. For example, U.S. Pat. No. 4,622,764 discloses a molded shell made of a rigid material, such as a rigid plastic or metal, so as to reinforce the rear portion of the shoe. The molded shell is placed at the outer side of an upper and a lasted insole, and is assembled with the upper after the upper is lasted. As both of the molded shell and the insole have planar top and bottom faces, they do not conform to the wearer""s heel.
To comfort the wearer""s foot, it is conventional to place inside a shoe a removable foot pad which is concave at the top face thereof to match the convex bottom of the wearer""s heel. However, although the foot pad is thick at the lateral parts thereof, the central concave part of the foot pad is usually thin and does not have enough thickness to cushion the convex part of the wearer""s heel since the total thickness of the foot pad is limited by the height of the interior space of the shoe which is determined by a last used in manufacturing the shoe. If the foot pad is too thick, it would affect the originally predetermined dimensions of the interior space of the shoe.
An object of the present invention is to provide a shoe with an ergonomic insole unit which has a concave support face to match the contour of the convex bottom of the wearer""s heel and which still permits a conventional heel lasting machine to perform a heel lasting operation though using a last with a heel section conforming to the wearer""s heel.
Another object of the present invention is to provide a shoe with an ergonomic insole unit which has a concave support face to match the contour of the convex bottom of the wearer""s heel and which still has a concave part with a thickness sufficient to cushion the wearer""s heel.
Still another object of the present invention is to provide a shoe with an ergonomic insole unit which has a concave support face to match the contour of the convex bottom the wearer""s heel and which can still be united with a conventional outsole that can be mass-produced.
Accordingly, a shoe according to the present invention comprises an ergonomic insole unit, and an upper having a top end disposed above the insole unit and a bottom margin attached directly to the insole unit, the insole unit including a heel part which includes a base and a rear upward flange projecting upward from a periphery of the base and making a U-shaped turn around the base, the upward flange extending inwardly of the bottom margin of the upper, the base having a planar bottom face,the rear upward flange having an outer surface extending upward from the planar bottom face of the base and forming a corner with the planar bottom face, the heel part further having a concave inner surface opposite to the outer surface and the bottom face, the inner surface extending gradually upward and outward along a direction from a mid part of the base to a top end of the upward flange and having a curved face extending along the corner, the heel part having, between the planar bottom face and the inner surface, a thickness which decreases gradually from the upward flange toward the mid part.